Apollo - The scientific payoff.
A great deal of information regarding the composition and the age of the lunar surface has been obtained as a result of the Apollo mission. It has been found that the moon cannot have evolved as a cold planet, but had a history of intense and voluminous volcanism for the first 1.5 billion years of its life. The moon appears to have cooled rapidly at some stage soon after three billion years ago. The evidence indicates that the lunar mantle is solid down to at least 800 km.
Ridley, I.↗